Drill bits for subterranean drilling, such as drilling for hydrocarbon deposits in the form of oil and gas, conventionally include internal passages for delivering a drilling fluid, or “mud,” to locations proximate a cutting structure carried by the bit. In fixed cutter drill bits, or so-called “drag” bits, the internal passages terminate proximate the bit face at locations of nozzles received in the bit body for controlling the flow of drilling mud used to cool and clean the cutting structures (conventionally polycrystalline diamond compact (PDC) or other abrasive cutting elements). Some drill bits, termed “matrix” bits, are fabricated using particulate tungsten carbide infiltrated with a molten metal alloy, commonly copper-based. Other drill bits, termed “cemented” bits, are fabricated by sintering particulate tungsten carbide and a metal or metal alloy, commonly cobalt- or nickel-based. Still other drill bits comprise steel bodies machined from blanks, billets or castings. Steel body drill bits are susceptible to erosion from high pressure, high flow rate drilling fluids, on both the face of the bit and the junk slots, as well as internally. As a consequence, on the bit face and in other high-erosion areas, hardfacing is conventionally applied. Within the bit, erosion-resistant components such as nozzles and inlet tubes fabricated from tungsten carbide or other erosion-resistant materials are employed to protect the steel of the bit body. “Matrix” bits and “cemented” bits are less susceptible to this erosion, but still require nozzles for directing desired fluid flow.
As shown in FIG. 1 of the drawings, a conventional steel body drill bit 10 for use in subterranean drilling may include a plurality of nozzle assemblies, exemplified by illustrated nozzle assembly 12. While many conventional drill bits use a single piece nozzle, the nozzle assembly 12 is a two piece replaceable nozzle assembly, the first piece being a tubular tungsten carbide inlet tube 14 that fits into a port 16 machined in the body of the drill bit 10, and is seated upon an annular shoulder 18 of port 16. The second piece is a tungsten carbide nozzle 20 that may have a restricted bore 22 that is secured within the port 16 of the drill bit 10 by threads which engage mating threads 24 on the wall of the port 16. The inlet tube 14 is retained in passage 26 by an abutment between the annular shoulder 18 and the end of the nozzle 20. Further, the outer surface or wall of the nozzle 20 is in sealing contact with a compressed O-ring 28 disposed in an annular groove formed in the wall of port 16 to provide a fluid seal between the bit body 30 and the nozzle 20.
Because of the importance of the cooling and cleaning functions of the drilling fluid, others in the field have attempted to optimize these benefits by specifically orienting the nozzle bore to direct the spray pattern of the drilling fluid to a predetermined location on a cutting surface of the bit. In still other applications designers have used computational fluid dynamics (“CFD”) to model fluid as it flows across the drill bit to help determine desirable placement of the nozzles upon the bit body.
The limited ability to control drilling fluid emanating from a nozzle in a desired fashion necessarily limits the potential efficiency of the cleaning and cooling functions of the drilling fluid. Further, since conventional nozzles direct a spray pattern, in the shape of a cone, of drilling fluid along a single direction or path at a relatively high velocity, impingement of the drilling fluid emanating from a conventional nozzle upon a portion of the drill bit, i.e., a blade or other portion of the bit body, may cause excessive erosion or wear to occur. Particularly, in the case where a nozzle is designed for providing a single flow stream of drilling fluid toward multiple paths, such as toward two junk slots, excessive erosion and wear may occur on the leading end of the structure, e.g., blade, separating the single flow stream into the multiple paths.
Thus, it would be advantageous to provide a nozzle for use in subterranean earth-boring drill bits, which provides suitable cuttings removal impetus, but which reduces undesirable erosion of the drill bit within which the nozzle is installed during use. It would also be advantageous to provide a nozzle design that allows tailoring of the distribution of drilling fluid emanating from the nozzle. Additionally, it would be advantageous to provide a nozzle design that may provide a suitable main cone spray pattern, as well as a secondary spray pattern proportioned to direct the fluid flow to specific areas of the drill bit, particularly toward areas that may experience cuttings buildup, or heat, while advantageously reducing the abrasion, and wear upon the drill bit conventionally caused by direct impingement thereon by a single fluid stream.